1. Field of the Invention
The present invention relates to a semiconductor device and a fabricating method thereof, and particularly relates to an image sensor and a fabricating method thereof.
2. Description of Related Art
An image sensor is an electronic device, which converts optical information into electrical signals. Image sensors are roughly divided into two different categories, Cathode Ray Tube (CRT) and fixed photograph device. CRT is mainly applied in television (TV) and widely used for applying image processing techniques in measuring, controlling, and recognizing application techniques. At present, there are two types of fixed photograph devices, including a charged coupled device (CCD) and a complementary metal-oxide-semiconductor (CMOS).
A complementary metal-oxide-semiconductor (CMOS) image sensor is a device, which converts optical images into electrical signals through CMOS fabricating technique. Compared with a CCD image sensor which has been widely used, a CMOS image sensor has the advantages of simple driving method, various scanning methods, single-chip signal processing circuit, lower production costs, and lower power consumption. For the above advantages, CMOS image sensors become more widely applied than CCD image sensors in recent years.
However, many problems still exist in the processes of fabricating CMOS image sensors, and they impair the quality of CMOS image sensors.
For instance, an opening which exposes a pad is formed before the formation of a color filter array (CFA) and U-lenses, so as to perform a wafer acceptable test. Succeeding fabricating processes will be performed after a wafer is tested. It is noted that, when a photoresist material is applied to form the color filter array, the opening exposing the pad will cause the uneven coating or residuals of the photoresist material, which reduces the image quality of the CMOS image sensor.
In addition, the color filter array is generally formed on a silicon nitride passivation layer. However, the adhesion between the silicon nitride passivation layer and the color filter array formed by the photoresist material is not good enough and usually causes the peeling of color filter units in the color filter array. Furthermore, the developing process and the rework process for forming the color filter array both bring damage to the pad exposed by the opening.